In order to reduce the risk in endoscopic surgery of injury to blood vessels or internal organs through puncture, the so-called Veres needle is used. The Veres needle has a hollow outer cannula that is ground obliquely at its distal end to a sharp, penetrating point. A protective element is mounted in the cannula which can be shifted axially and is a spring element that has a closed, blunt, only slightly arched protective surface at its front, distal end. The protective element function as a tube for the insufflation of gas with an opening mounted on the side behind the distal tip.
The Veres needle preferably is used in endoscopic abdominal surgery to introduce pneumoperitoneum in the first puncture. For this, a small incision is first made in the skin, the Veres needle is then introduced into the subdermal fatty tissue, and the protective element is pressed distally forward through the force of the spring, because the resistance in the subdermal fatty tissue is less than the force of the spring. The blunt protective surface of the protective element projects distally forward over the sharp tip of the hollow cannula and displaces the subdermal fatty tissue bluntly, so that no vascular injuries occur in the subdermal fatty tissue due to the sharp, penetrating tip. If the fascia is reached, the resistance of the tissue increases greatly and becomes greater than the force of the spring that presses the protective element forward. The protective surface of the protective element recedes behind the sharp tip and the latter can now penetrate the fascia. Immediately after penetration of the fascia, the counterpressure of the tissue drops again, so that the force of the spring can then shift the protective element forward, and the protective surface protects the sharp tip in the area of the preperitoneum again. As soon as the peritoneum is reached, the pressure against the tip increases again so that the protective element with the protective surface again is pushed back and the sharp tip can open the peritoneum As soon as the tip slides forward into the abdominal cavity, the protective element again rushes forward under the force of the springs because the free abdominal cavity offers no resistance The blunt protective surface, therefore, protects the vessels and intestine in the free abdominal cavity from injury by the sharp tip.
With the Veres needle, the penetration of the fascia and the peritoneum is recognized in that the protective element is pushed backwards and after penetration again rushes forward. This known Veres needle also has a considerable residual risk. For example, intestinal loops adhering to the wall of the peritoneum and large vessels lying in the area of the retroperitoneum in certain circumstances may not be noticed, because the sharp tip, immediately after penetrating the peritoneum, penetrates these intestinal loops or vessels without the protective element being able to quickly move forward.
This residual risk is reduced by a needle of the nature of the generic terms as recognized in German No. 9,112,976 U1 and similarly in U.S. Pat. No. 4,254,762. In the case of this needle, the protective element that can be shifted in the cannula tube provided with the sharp tip is formed as a tube and has at its distal, front end a translucent, blunt protective surface An optical system is installed in the tubular protective element by which the protective surface can be observed from inside. The protective element, therefore, not only fulfills the function of protection as with the conventional Veres needle, but in addition, makes an optical observation of the tissue layers penetrated possible for the operator of the needle, and thus, the possibility of checking whether the free abdominal cavity is actually reached after penetration of the abdominal wall. In the case of this known needle, however, the distal protective surface of the protective element is constructed as an even front face running vertically to the axis of the cannula. If this even protective surface is applied to the tissue under the pressure of the force of the spring, the tissue will be pressed flat, so that no optical differentiation is then possible between fatty tissue, fascia, and muscle tissue Although this is to be prevented in that during the puncture, the flat protective surface moves back behind the sharp tip of the cannula tube, so that a free space remains between the tip and the protective surface, this free space fills with blood during the puncture, so that differentiating observation is also not improved in this manner.
Furthermore, a trocar is known, see German 4,035,146 C2 , whose penetrating tip is made as a transparent window. An optical system inserted into the trocar shaft allows observation both of the tissue lying directly in front of the tip as well as of the tissue lying to the side of the tip when the trocar tip penetrates. The operator, therefore, can penetrate the tissue in view. This trocar, however, has a relatively large external diameter. In the case of thin needles of only 2-3 mm external diameter, it is difficult to produce a transparent tip with the mechanical properties required for the penetration.
From EP 0,684,016 A2 and EP 0,642,764 A1, a trocar is known in which the distal tip is rounded and transparent. The penetration of the tip into the tissue can be observed via an optical system installed in the trocar. Since the rounded tip of the trocar is not suitable for penetration of the tissue, sharp edges are mounted in the tip which can be moved distally forward beyond the rounded, transparent trocar tip in order to separate the tissue to be penetrated. This produces the disadvantage that in the actual penetration possible by means of the distally extended cutting edges, no observation is possible.
The objective of the invention is to provide a medical needle that has a sharp, penetrating tip in which the risk of injury to vessels and organs by the sharp, penetrating tip is as low as possible.
The surgical needle herein disclosed has a sharp, penetrating tip with a protective element that can be shifted by spring actions whose distal, blunt protective surface is rounded and is optically transparent An optical system is installed in this protective element by which the protective surface can be observed from the inside.
The optical system is mounted in the protective element such that the distal lens of the system is at a distance axially from the transparent protective surface so that a good optical image of the tissue parts lying on the protective surface results. The optical system can be fixed in the protective element or mounted so that it can be changed in the protective element. An exchange mounting has the advantage that the needle can be constructed as a disposable instrument whereas the expensive optical system can be used several times. Also in the case of the disposable instrument, the exchangeability of the optical system may be of advantage because the optical system can be taken out for sterilization of the needle, and must not be exposed to the high sterilization temperatures
The blunt protective surface shields the sharp tip in the distally shifted position of the protective element as well as possible, because the sharp, penetrating tip lies on the cylindrical casing surface of the protective element so that the tip does not project freely in spite of the rounding of the protective surface.
The shapes of the blunt protective surface of the protective element can be made different according to the requirements of different uses. A flat protective surface arched slightly forward provides larger surface bearing on the tissue so that a greater tissue pressure, working against the force of the spring, is exerted on the protective element.
The effect of the changing tissue resistance exploited in the conventional Veres needle can also be used in this constructed.
A more intense arching of the protective surface forward with a smaller curve radius may be advantageous from other perspectives. The smaller curve radius and more intense arching of the protective surface result in lower counterpressure of the tissue on the protective surface and the protective element in the penetration process. The lower pressure of the protective surface on the tissue has the consequence that the tissue becomes less anemic, that is, that the blood is less pressed out of the tissue, in which case the tissue would appear pale. Furthermore, the protective element with the blunt protective surface arched forward can also be intentionally pressed forward and held in the forward position in order to probe forward with the tip in the tissue while viewing, and the sharp, penetrating tip can then be used, with release of the protective element, only when it is assured that the penetration will be without danger.
During the penetration and insertion of the needle, the subdermal fatty tissue first appears yellow When the fascia is reached, it appears white. After penetration of the fascia, the muscle tissue appears red Any vessels lying in front of the tip of the needle can be recognized and avoided. If the preperitoneal fatty tissue is reached, the protective element with the blunt protective surface can intentionally be pressed forward so that the blunt protective surface, independent of the force of the spring, can be kept projecting beyond the sharp tip. The fatty tissue can be penetrated with the blunt protective surface until the protective surface contacts the wall of the peritoneum. The latter can be pressed in with the blunt protective surface without penetration, and stretched (tenting effect). In this way, the peritoneum becomes semitransparent and intestinal loops or vessels adhering to the peritoneum can be recognized.
When it can be assured in this manner that no adhesions are present beneath the peritoneum, the protective element can be released so that it recedes back behind the sharps penetrating tip. The sharp tip then penetrates the peritoneum without risk.